Stat > DOE > Modify Design > Taguchi > Specify
Allows you to ignore an existing signal factor and treat the design as non-dynamic. You can also add new levels to an existing signal factor.
Modification
Ignore signal factor (treat as non-dynamic): Choose to ignore the signal factor in the design and treat the design as non-dynamic.
Add new levels to signal factor: Choose to add new levels to an existing signal factor. Enter the new signal factor levels in the box.